This document focuses on the memory layout at the instant that BIOS gives control over to the first
446 bytes of the MBR.
http://www.cs.fsu.edu/~baker/devices/lxr/http/source/linux/Documentation/i386/boot.txt?v=2.6.25.8#L46
http://www.syslinux.org/wiki/index.php/Memory_Map_(Segment_0)
http://en.wikibooks.org/wiki/X86_Assembly/Bootloaders#Technical_Details
Other information about the initial boot environment
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http://wiki.osdev.org/Boot_Sequence